The Effect of Biological Control Agents on Fungi Isolated from some Citrus Trees in Mosul

In this study, the counter effect of two Biological Control Agents, namely Trichoderma harzianum fungi and Bcillus subtilis bacteria against the fungi-like organism Phytophthora infestans and the fungi; Fosarium solani and Rhizoctonia solani isolated from orange- trees bark and from lemon- trees roots. The results showed that the counter effect of T. harzianum (using double culture on petri dishes) reached 1.0 according to Bell scale, against all these pathogens. The counter effect of this antibiotic was also tested in vitro on branches taken from citrus trees and infected with Phytophthora infestans. The infection percentagesbefore treatment with T. harzianum were 75% and 58.3% for the branches isolated from lemon trees and orange trees respectively, whereas after treatment with the inhibition fungi, the percentages of infection were 25% and 16.6% for the branches isolated from lemon trees and orange trees respectively. The percentages of inhibition by Bacillus subtilis bacteria were 83%, 71% and 73% against Phytophthora infestans , Fusarium solani and Rhizoctonia solani respectively